1. Field of the Invention
The present invention relates to an electronically controlled cooking apparatus and more particularly to an electronically controlled cooking apparatus such as a microwave oven in which humidity in a heating chamber is detected by using a humidity sensor and food is heated dependent on the detected humidity.
2. Description of the Prior Art
It is known in the prior art that an electronically controlled cooking apparatus such as a microwave oven detects humidity in a heating chamber by using a humidity sensor and heats food dependent on the detected humidity. Such a cooking apparatus using a humidity sensor is disclosed for example in Japanese Patent Publication No. 3171/1983, 10738/1986 or 5248/1987.
However, in such a conventional cooking apparatus, it is sometimes difficult to heat food in good condition for the below described reasons.
(1) If food to be heated is covered with clear-plastic wrap, it is considerably difficult to detect reliably humidity changes caused by heating.
(2) In general, heating control patterns differ variously dependent on a quantity of food to be heated, a shape of a vessel containing the food or a shape of its lid and, accordingly, considerable difficulty is involved in appropriately applying a suitable heating control pattern based on a detected humidity.
(3) Even if the same cooking method is applied, the way in which vapor is generated from food in a heating chamber considerably differs dependent on various factors such as the quantity of food to be heated and the manner of placing a cover on a container and, consequently, if heating of the food is controlled dependent on the detected humidity according to the same cooking sequence, a satisfactory result of cooking cannot always be obtained.
(4) If an initial temperature of food is high or a very small quantity of food is to be cooked, the food is rapidly heated to an excessively high temperature before a suitable heating control pattern is determined based on detection of a humidity change in heating, which entails a danger of firing.
The U.S. Pat. No. 4,484,065 discloses a heating apparatus which determines whether a heated object is covered tightly or not, dependent on a change rate of humidity in a heating chamber and selects a suitable heating sequence based on the determination. However, in such a heating apparatus, the humidity change rate is detected only once at an early stage of heating and determination as to a covered state and selection of a heating pattern to be applied thereafter are made only based on the result of this single detection. Accordingly, it is difficult to apply fine heating control to obtain a good result of cooking.